Electrical contact



Patented June 10, 1952 ELECTRICAL CONTACT Renzo U. Volterra, Attleboro,Mass., assignor to.

Metals & Controls Corporation,

Attleboro,

Mass, a corporation .of Massachusetts No Drawing. Application September11, 1946, Serial No. 696,361

This invention relates to electrical contacts and methods of making:such contacts and more particularly to composite metal electricalcontacts.

Among the several objects of the invention may be noted the provision ofcomposite electrical contacts that have high current carrying capacityand great mechanically strength, the provision of composite electricalcontacts that have high melting points and are non-sticking, theprovision of contacts of the class to be described which may beinexpensively manufactured, and the provision of a method formanufacturing contacts of the class indicated which is simple, efficientand economical. Other objects will be in part apparent and in partpointed out hereinafter.

The invention accordingly comprises the ingredients and combinations ofingredients, the proportions thereof, steps and sequence of steps, andfeatures of composition and manipulation, which will be exemplified inthe products and methods hereinafter described, and the scope of theapplication of which will be indicated in the following claims.

Electrical contacts for breaking high current circuits must bemechanically strong, good electrical conductors, able to withstand highintensity arcs without sticking and pitting, relatively non-oxidizable,and have a high melting point and 'long life. Electrical contacts with acontacting layer of ruthenium on a highly conductive metal base have allof these valuable qualities and in addition can be advantageously usedto make and break alternating current circuits of high frequency.

Although ruthenium is an excellent material for electrical contactsurfaces it is extremely expensive. In accordance with the presentinvention it has been found that an inexpensive contact may be made ifruthenium is used as a thin layer on a highly conductive, and lessexpensive metal. A surface of ruthenium may be conveniently formed onsuch a conductive metal by electrolysis. Although the contacting surfaceof such an electrical contact is relatively pure ruthenium which isexpensive, in an ordinary contact, an extremely small amount is used.For example, the surface is most conveniently secured by electroplatingruthenium on the conductive metal to a thickness of .0001 inch.

A process of electroplating ruthenium on a less expensive and conductivemetal such as silver can be generally described as follows. Ruthenium isfused with an alkali peroxide and 6 Claims. (Cl. 200-166) .niumhydroxide.

the resulting melt isthen dissolved in dilute hydrochloric acid. Thissolution upon treatment with an alkali bicarbonate will precipitate,ruthe- The ruthenium hydroxide is then separated from the supernatantliquid and heated with sulfamic acid. The resulting product which isprobably ruthenium sulfamate, is diluted with water and is used as theelectrolyte. An unplated silver contact is used as the cathode and isimmersed in this electrolyte and current passed thru the solution. Ithas been found that at a potential of 2.5 volts a current density of 15amperes per square foot can be used without any excessive development ofhydrogen. The anode used in the process may be made of any desiredmaterial.

The following specific example is illustrative of the invention Example1 Two grams of metallic ruthenium were fused in a crucible with 5 gramsof sodium peroxide. The melt was dissolved in 50 ml. of water and ml. ofhydrochloric acid. A deep orange solution was obtained which when heatedwith sodium bicarbonate gave a precipitate of ruthenium hydroxide. Theruthenium hydroxide was heated with 5 grams of sulfamic acid on a steambath. This solution was then diluted to 500 ml. and was used as theelectrolyte. The ruthenium was plated on the silver metal contact baseat an E. M. F. of 2 volts and a current density of 15 amperes per squarefoot.

As a further economy measure ruthenium may be plated only on thecontacting surface or on the contacting surface and all or part of theside surfaces of the contacts.

The ruthenium plated contacts of the present invention can beadvantageously used to make and break alternating current circuits ofhigh frequency and are mechanically strong, good electrical conductors,can withstand high intensity arcs without sticking and pitting, arerelatively non-oxidizable, and have a high melting point and long life.

In view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results attained.

As many changes could be made in the above methods and products withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description shall be interpreted asillustrative and not in a limiting sense.

I claim:

1. In combination with an electrical device for making and breaking highcurrent carrying circuits, a high melting point non-sticking compositeelectrical contact of a highly conductive metal with a relatively thincontacting surface of ruthenium.

2. In combination with an electrical device for making and breaking highcurrent carrying circuits, a high melting point non-sticking compositeelectrical contact of silver with a relatively thin contacting surfaceof ruthenium.

3. In combination with an electrical device for making and breaking highcurrent carrying circuits, a high melting point non-sticking compositeelectrical contact of a highly conductive metal with a relatively thincontacting surface of ruthenium, the thickness of the ruthenium layerbeing approximately .0001 inch.

4. In combination with an electrical devic for making and breaking highcurrent carrying circuits, a high melting point non-sticking compositeelectrical contact of silver with a relatively thin contacting surfaceof ruthenium, the thickness of the ruthenium layer being approximately.0001 inch.

5. In combination with an electrical device for making and breaking highcurrent carrying circuits, a high melting point non-sticking compositeelectrical contact comprising a relatively thin contacting layer ofelectroplated ruthenium on a highly conductive and less expansive metal.

6. In combination with an electrical device for making and breaking highcurrent carrying circuits, a high melting point non-sticking compositeelectrical contact comprising a relatively thin contacting layer ofelectroplated ruthenium on silver.

RENZO U. VOLTERRA.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

3. IN COMBINATION WITH AN ELECTRICAL DEVICE FOR MAKING AND BREAKING HIGHCURRENT CARRYING CIRCUITS, A HIGH MELTING POINT NON-STICKING COMPOSITEELECTRICAL CONTACT OF A HIGHLY CONDUCTIVE METAL WITH A RELATIVELY THINCONTACTING SURFACE OF RUTHENIUM, THE THICKNESS OF THE RUTHENIUM LAYERBEING APPROXIMATELY .0001 INCH.